Patent GB-190307789-A (GB)
Title: Improvements in Telephone Systems.
Inventor: PAUL THOMAS
Filed: 1903-04-03
Granted: 1903-08-27
Abstract: 7789. Paul, T., and McDougall, J. L. April 3. Telephone systems; telephone calls.-Relates to exchange systems with a central calling-battery, and also to central-energy systems. Fig. 3 shows the connections between two subscribers and the exchange. The subscribers' receivers R, R<2> are connected in parallel with the secondaries I<2> of the induction coils. The primaries I<1> are in series with the transmitters T and local batteries L. Signalling-instruments B, B' are provided at the subscribers' stations. Assuming that subscriber 37 wishes to speak to subscriber 68, the following operations are necessary :-Subscriber 37 lifts his receiver from the switch hook S and thus closes the following circuit :-line l, jack spring M, metallic strip D (the plugs P, P<1> and flexible connection Q being absent), connection X, battery V, indicator I (common to all the subscribers), exchange operator's switch hook S', line l<1>, and induction coil I<2>. In consequence of the opera tion of the indicator or annunciator I, the exchange operator lifts his receiver R<1> from the hook, and thus closes a talking-circuit through the lines l. Having ascertained that No. 37 has called, and that he wishes to speak to No. 68, the operator inserts plug P<1> into the socket of No. 68, thus making contact with the jack spring M and breaking its connection with the metallic strip D. The operator then brings plug P into contact with contact-plate C, and draws the plug across into contact with the plate E. The first contact closes the circuit of the batteries U, V through the calling-wire G, bell B', switch hook S, line l, and plugs P', P, thus ringing up subscriber 68. The second contact closes a talking-circuit through the conductor X, plugs P, P', line l, switch hook S<2> (which has been released by subscriber 68 lifting his receiver), induction coil I<2>, line l<1>, switch book S<1>, and operator's induction coil. The operator having ascertained that his call has been responded to, places the plug P in the socket of No. 37, and communication is established between the two subscribers through the lines l, P. When either subscriber hangs up his receiver, the annunciator I drops, and the operator is notified that the conversation is completed. If the operator prematurely removes a plug, either the annunciator drops, or he is put into speaking connection with the subscriber from whose socket the plug has been removed, according as his receiver is in use or not. If a separate annunciator is used for each subscriber, it is placed between the spring M and the strip D, so that it is not introduced into the speaking circuit. Fig. 5 shows a central-energy system. In this case the transmitters 8 and primary windings 5 are placed in the line circuit, the receivers 7 and secondary windings 6 being in a local circuit. The indicator 14 is operated by the battery 15, and the operator speaks to a calling-subscriber by aid of the battery 30. The operator calls up a subscriber by drawing a plug along a corrugated plate 33, which corresponds to the plate C, described above, the batteries 15, 15<a> serving to ring up in series. The battery 46 is the speaking-battery both for exchange to "called-up" subscriber, and for the established connection shown in Fig. 5. Premature interruption of the talking-circuit is notified to the operator in the manner described with reference to Fig. 3.